Numerous solids (>30) reportedly exhibit high efficiencies for photocatalysis of H2O (and generation of hydrogen) at ultraviolet wavelengths, including NaTaO3 (56%; quantum yield), Sr2Nb2O7 (23%), La2Ti2O7 (27%), and La4CaTi5O17 (20%). (Kato, H.; Kudo, A. Catal. Lett. 1999, 58(2,3), 153; Kudo, A. et al., J. Phys. Chem. B 2000, 104, 571; Kim, H. G. et al., Catal. Lett. 2003, 91, 193; Kim, H. G. et al., Chem. Comm. 1999, 1077). These are typically impregnated with co-catalysts such as Pt and RuO2 to assist H2/O2 formation, and are then suspended and illuminated in H2O. During the photocatalytic reaction several requirements must be met, including, a) the photon energy must be greater than the band gap, b) the excited electrons and holes must be separated, such as by the surface/electrolyte polarization, c) the conduction band must be higher than the reduction potential of H2O (0.0 eV) and the valence band lower than the oxidation potential of H2O (−1.23 eV) (i.e. absorbed light has λmin<1000 nm), and d) the surfaces should be photostable. For optimum performance, the band gap should be small enough (˜1.5-2.0 eV) to absorb a large fraction of the solar energy. However, while many metal-oxide solids have shown to be photostable (d) in aqueous solutions, it has proven challenging to lower their band gap to absorb a greater fraction of incoming sunlight while keeping the conduction band above the H2/H2O redox couple (c) (“Energy Resources through Photochemistry and Catalysis (Ed.: M. Grätzel)”, Academic Press, New York, 1983).